"They're Coming" ?? Jacobs Last words...Who are They ??

This is one of those deliberate cliffhangers put in by the writers to keep the audience speculating over the break between seasons. The way i see it, is that "They" refers to one of two groups. The first being Jack, Kate and the rest of the 70's gang. The second being Ilana and her badass crew, who bring with them the real John Locke. Either of these groups ariving would cause a mild inconvenience to fake-locke and whatever his big plan is...

My guess was that Jacob meant Jack, Kate, Sawyer, Sayid, and everyone else that he touched in the flashbacks. It makes sense to me because, like I said, he made a point to touch each of them, so I feel like he'd be more likely to know something about them then any other "they" on the Island (or off, I guess), you know?

As for him "knowing" that this is going to happen, I always figured it was because it's happened before in some way. They're all stuck in some kind of time loop, but Jacob and "the Dark Man"/"Not-Locke" seem to be the only two that remember what happened in each loop. He knew because it's happened before, but he's the only one who remembers.

At least, that's my theory, lol.